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Temperature‐Dependent Surface‐Enrichment Effects of Imidazolium‐Based Ionic Liquids
Author(s) -
Kolbeck Claudia,
Deyko Alexey,
Matsuda Takashi,
Kohler Florian T. U.,
Wasserscheid Peter,
Maier Florian,
Steinrück HansPeter
Publication year - 2013
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201300719
Subject(s) - ionic liquid , x ray photoelectron spectroscopy , alkyl , chemistry , analytical chemistry (journal) , phase (matter) , phase transition , organic chemistry , chemical engineering , catalysis , thermodynamics , physics , engineering
We present the first systematic study of the influence of temperature on the degree of surface enrichment of 1‐alkyl‐3‐methylimidazolium‐based ionic liquids (ILs). Using angle‐resolved X‐ray photoelectron spectroscopy, we demonstrate that the degree of surface enrichment strongly decreases with increasing temperature for all the studied ILs. For ILs with the same cation, but different anions, [C 8 C 1 Im]Br, [C 8 C 1 Im][TfO] and [C 8 C 1 Im][Tf 2 N], no significant differences of the temperature‐induced partial loss of surface enrichment are found. Measurements for [C 4 C 1 Im][TfO], [C 8 C 1 Im][TfO] and [C 18 C 1 Im][TfO] indicate a small effect of the chain length. For [C 18 C 1 Im][TfO], a continuous decrease of alkyl surface enrichment is found with increasing temperature, with no abrupt changes at the phase‐transition temperature from the smectic A to the isotropic phase, indicating that the surface enrichment is not affected by this phase transition.